HPCL Mechanical Engineer Mock Test - 10 - Mechanical Engineering MCQ

The segment is in passive voice, thus only a verb in third form is eligible for the blank. Among all the given options, only ‘discovered’ fits the blank as the virus already existed in the monkeys but was found in 1970.

Hence, option D is correct.

Last 20 number = 12th to 31st
So remaining is 11th number.
So the answer = 31 × 57 – 10 × 50 – 20 × 61 = 47
Hence, Option D is correct.

Surface area of cube = 6 * Side of cube²  
Let a = side of cube.
a = 2m.
Surface area of cube = 6 * 2 * 2
     => 24 m² .
Hence option C is correct.

It's 1 because of a⁰= 1.
So 1×1/1 = 1

Sundays → 2nd, 9th, 16th, 23rd and 30th (5 Sundays)

Hence, Option C is correct.

Diameter of the circle = breadth of the rectangle = 42 meters
Radius of the circle

So the answer 

Hence, Option D is correct.

a = 1/ (3-2√2) 

b =  1/ ( 3+2√2) 

∴ ab =  1/(3-2√2) * 1/ (3+2√2) 

=>  1/ (9-8) 

=> 1 

We know; 

(a+b)² = a² + b² + 2ab

And, a²+ b² = (a+b)² - 2ab

=> [ 1/(3-2√2) + 1/(3+2√2) ]² -2*1

=> [3+2√2+3-2√2 / 1]^2 -2 

=> (6)² - 2 

=>  36 - 2
=>  34

As Silence is opposite to noise, similarly Baldness is opposite to Hair.

Ascending order:
686,   719,   765,   795,   815,   822,   835

Middle Number

Middle digit of 795 is 9.

Carpenter, Plumber, Electrician and Blacksmith are in same working category.

The logic follows here is:

It is given that Rahul has 48% marks in 10th, an age of 28 years, and work experience of 5 years.

It is clearly mentioned in the criteria that 10^th marks should be greater than 50% for job P and greater than 60% for job Q. Rahul got 48% marks in 10^th.

Therefore, Rahul, neither qualifies for job P nor for job Q.

Hence, the correct answer is "Neither P nor Q".

Punching/Blanking: Punching or blanking is a process in which the punch removes a portion of material from the larger piece or a strip of sheet metal. If the small removed piece is discarded, the operation is called punching, whereas if the small removed piece is the useful part and the rest is scrap, the operation is called blanking.

Piercing: It is a process by which a hole is cut (or torn) in metal. It is different from punching in that piercing does not generate a slug.

Perforating: It is an operation in which a number of uniformly spaced holes are punched in a sheet of metal. The holes may be of any size or shape. They usually cover the entire sheet of metal.

Nothing: It is an operation in which a specified small amount of metal is cut from the edges.

Lancing: It is an operation of cutting a sheet metal through a small length and then bending this cut portion.

Work = electrical work

=3×100W

=3×100×10×60J

Work (W)=180kJ

Heat transfer, Q=0 (no heat transfer from/to battery)

Coining is essentially a cold‐forging operation except that the flow of the metal occurs only at the top layers and not the entire volume. In the coining process, compressive forces are there.

In blanking, the piece being punched out becomes the workpiece, and any major burrs or undesirable features should be left on the remaining strip. Blanking is a shearing operation.

Drawing when cup height is more than half the diameter is termed deep drawing. During deep drawing, in the flange of blank, there is bi‐axial tension and compression stresses.

Checking according to given options.

P = hρg

a) ⇒ 10.2 m of fresh water (ρ = 998 kg/m³)

P = 10.2 × 998 × 9.81 = 99861.87 Pa = 99.861 kPa

b) ⇒ 10.1 m of saline water (ρ = 1025 kg/m³)

P = 10.1 × 1025 × 9.81 = 101.558 kPa

c) ⇒ 12.5 m of kerosene of ρ = 800 kg/m³

P = 12.5 × 800 × 9.81 = 98.1 kPa

d) ⇒ 6.4 m of carbon tetrachloride of ρ = 1590 kg/m³

⇒ 6.4 × 1590 × 9.81 = 99.826 kPa

So option b is nearest, so correct

Properties of HSS:

• High working hardness

• High wear resistance

• Excellent toughness

• High retention of hardness and hot hardness.

The energy required to raise a mass of 1 centigrade (K or ºC) is the specific massic heat of the substance, multiplied by its mass and 1 centigrade. In the case of 1 kilogram of water: E = (4180 J/(kg×K)) ×1 kg × 1K = 4180 J. You can also use the specific molar heat with the number of moles.

Cementite: Cementite or Iron Carbide has the chemical formula Fe3C and contains 6.67% carbon by weight. It is the hardest structure that appears in the iron-carbon equilibrium diagram. Cementite has an orthorhombic crystal structure and is extremely hard and brittle as compared to austenite and ferrite.

Martensite: It is a metastable phase of steel formed by the transformation of austenite below 320°C. Martensite is an interstitial supersaturated solid carbon solution in α – Iron and has a body-centred tetragonal lattice. It has a carbon content of up to 2% and is extremely hard and brittle. It is a product of rapid cooling (quenching) and possesses an acicular or needle-like structure.

The hardness of steel depends upon the amount of cementite. Martensite was obtained after hardening treatment of steel.

Steels with low carbon content do not respond appreciably to hardening treatment because the main constituent is soft ferrite. If hypo-eutectoid steel is cooled rapidly, martensite is formed.

Fuel gas analysis refers to the determination of the composition of exhaust gases. It can be done theoretically and experimentally.

Various devices available for measuring the composition of products of combustion (flue gas) are Orsat Analyzer, Gas chromatograph, Infrared analyzer, and Flame ionization detector, etc.

Orsat Apparatus: It is used for carrying out volumetric analysis of dry products of combustion.

Bomb Calorimeter: It is used to determine the higher calorific value of solid and liquid fuels.

Barometer: A barometer is used to measure local atmospheric pressure.

Rope dynamometer: A rope brake dynamometer is used to test the power of engines.

As the hot coffee remains hot for a long time so neither heat nor mass is exchanged with the surroundings and hence it is an example of isolated system.

Lean mixture: Mixture which contains more air than the stoichiometric requirement. There is more oxygen than required to burn the amount of fuel completely; after combustion, there is excess oxygen in the exhaust gases.

Rich Mixture: Mixture which contains less air than the stoichiometric requirement. There is not enough air to completely burn the amount of fuel; after combustion, there is unburnt fuel in the exhaust gases.

Spark advance/Ignition Advance:

The purpose of the spark advance mechanism is to assure that under every condition of engine operation, ignition takes place at the most favorable instant in time, i.e., most favorable from the standpoint of engine power, fuel economy, and minimum exhaust dilution. By means of these mechanisms, the advance angle is accurately set so that ignition occurs before the TDC point of the piston.

Ignition timing is the correct instant for the introduction of a spark near the end of the compression stroke in the cycle. Several factors affect the ignition timing of an engine, like compression ratio, Engine speed, Engine load, Quality of fuel, Mixture strength, etc.

In the case of a rich mixture, the combustion rate is faster and less ignition advanced is required. And in the case of a lean mixture, the combustion rate will be slower, thus requiring more ignition advances.

When ignition occurs early in the compression stroke, the engine is said to be advanced. A retardation ignition takes place when the piston is just near the compression stroke.

If the ignition is advanced too much, it will be completed before the end of the compression stroke. Under these conditions, the crankshaft and connecting rod will have to push the piston upward, compressing the gases. In such a case, the force might not be sufficient to overcome the pressure and the engine would stop or stall.

If the ignition is retarded too much, the combustion of fuel will continue during the power stroke of the piston (Expansion stroke), and the maximum pressure will not be developed. Less work will be obtained from heat energy. Under these conditions, comparatively more exhaust gases will be going out of the engine cylinder overheating the exhaust valve.

Conclusion:

Rich Mixture with ignition advance: It can complete before the compression stroke

Weak Mixture without ignition advance: Combustion can be found to proceed during the expansion stroke

The rich mixture should have retarded ignition advance, and the lean mixture should have more ignition advance.

Different processes of the Otto cycle are as follows:

Process 1-2: Isentropic compression

Process 2-3: Constant volume heat addition

Process 3-4: Isentropic expansion

Process 4-1: Constant volume heat rejection.

If the applied force exceeds this limit, the force of friction cannot balance it, and the body begins to move in the direction of the applied force. This maximum value of frictional force, which comes into play when a body just begins to slide over the surface of the other body, is known as limiting friction.

Friction Force:

f = μN = µ_s × mg

µs is known as the coefficient of static friction

So without knowing the value of µ_s, we cannot determine friction force.

Mandrel is used to hold a hollow bar or a bar with a bore wen turning between live centre and dead cente of a lathe. A moving mandrel is also used for tube drawing

For the same orifice at different height:

Q ∝ √h

In ECM, both the tool electrode and the workpiece are submerged in an electrically conductive electrolyte, usually an aqueous salt solution such as sodium chloride (NaCl) or sodium nitrate (NaNO₃). A constant potential is applied between the two electrodes ensuring the workpiece becomes the anode (positive electrode).